DESCRIPTION: (Applicant's Description) Mammography and physical examination are the only generally accepted screening tools available for breast cancer. Both are limited by the need to perform a diagnostic procedure to determine if the breast contains atypia or cancer. Present techniques to evaluate the breast for cancer comprise needle biopsies and procedures that encompass the entire lesion, including excisional biopsy and mastectomy. Each procedure has the risk of hematoma formation and infection. The former procedures are limited by sampling error, while the latter require an operative procedure, are costly and may raise concerns regarding cosmesis. Breast nipple aspiration, which provides nipple aspirate fluid (NAP), causes minimal or no discomfort, is noninvasive, quick, and provides both cells and extracellular fluid from the breast ductal epithelium, the cells which give rise to cancer. We are able to obtain NAP in over 99 percents of pre-and postmenopausal subjects, and have demonstrated that a biomarker in NAP is highly specific for the presence of residual cancer after excisional biopsy. Our objective is to assess if biomarkers in NAP can determine the benign or malignant nature of both nonpalpable and palpable breast lesions. If one or more biomarkers in NAP from women with an undiagnosed breast lesion proves to be highly sensitive and/or specific in determining whether precancer or cancer is present in the breast, then findings in NAP may allow the subject to forego an invasive diagnostic procedure and proceed directly to definitive surgery